Conventionally, in bearings for conveyor idler rollers (hereinafter, referred to as conveyor bearings), in order to provide dustproofness and waterproofness thereto, bearings are generally used which has a configuration as shown in FIG. 6 in which a labyrinth-shaped seal is combined to an external side of a shield-type deep groove ball bearing or an open-type ball bearing.
As shown in the same figure, a conveyor bearing 5 is made up of an inner ring 6 which is fitted on and fixed to a shaft 1 and an outer ring 7 which is disposed rotatably relative to the inner ring 6 via a plurality of balls 8. The outer ring 7 is fixedly fitted in a bearing member 3 which is fixed to an inner circumferential surface of an idler roller 2. A labyrinth seal 4 is fitted on and fixed to the shaft 1 in such a way as to be adjacent to the inner ring 6 at an external side of the inner ring 6 in an axial direction. A lip portion 4a at an outside diameter side of the labyrinth seal 4 is made to be brought into sliding contact with the bearing member. An internal portion of the labyrinth seal 4 is filled with grease.